hobbs.] LONGITUDINAL SECTIONS OF THE ISLAND. 29 
ALONG BROADWAY AND ELEVENTH AVENUE BETWEEN SEVENTY-SECOND 
AND DYCKMAN STREETS. 
This section (tig. 6), like the last, is along the line of the subway, 
and has been furnished the writer through the courtesy of the rapid 
transit commission. 
Its chief interest is in showing- the regular transverse breaks in the 
continuity of the surface — breaks which were long ago described by 
Stevens as lines of dislocation. At Manhattan street there is a deep 
transverse crevice tilled with gravel to a depth of more than 135 feet 
below the present grade (serial number 1202. p. 80). At 96th street 
also there is evidence that a filled crevice extends to a distance of 
about 100 feet below the bottom of the present valley (serial number 
1199, p. 80). The deep embay ment at 157th street marks a line south 
of which the rocks forming the upland project east for a distance of 
about one-eighth of a mile. It is also the line along which the mass 
of Fordham Heights abruptly terminates at Harlem River. The val- 
ley north of Washington Heights (fig. 6) is that of Shermans Creek, 
and north of this bars were driven by the engineers of the commis- 
sion, to moderate depths, without encountering rock. The break at 
Shermans Creek, and those at 157th street, Manhattan street, and 96th 
street include subequal space intervals. 
The above-described sections only partly display the peculiarly 
rugged configuration of the rock basement of Manhattan. Attention 
should be especially called to the revelations of the map (PI. I) as to 
the zigzagging course of the lower Hudson channel, below Weehaw- 
ken, and to the knob of gneiss which rises at the Battery from the 
downtown lowlands. 
